1. Field of the Invention
The invention relates to hydraulic elevators. More particularly, the invention relates to a pump and tank for a hydraulic power unit.
2. Prior Art
Hydraulic elevator systems are popular for lower rise applications since installation cost is generally lower than traction type elevator systems. The car of a hydraulic elevator system is displaced upwardly and downwardly within a hoistway by a piston disposed within a drive cylinder located at the base of the elevator hoistway. In order to provide pressurized fluid to the drive cylinder and, on demand, drive the piston and elevator car connected thereto upwardly, a pump and motor assembly is required. Commonly pump and motor assemblies of the prior art were maintained in a machine room wherein a large horizontally disposed tank contained the pump and motor therewithin and sufficient oil to both drive the elevator car to its highest intended stopping point and still cover the motor and pump. Such tanks are very large because of the amount of oil required to both drive the piston and keep the motor and pump submerged. A benefit of the prior art arrangement is that noise generated by the motor and pump is contained substantially to the machine room and therefore is insulated from the elevator car. Referring to FIG. 1, a prior art hydraulic power unit is illustrated in a schematic machine room. The device 10 is generally mounted upon a type of support 12 within room 14. Tank 16 occupies a large portion of the machine room 14. The motor 18 and pump 20 are illustrated as mounted within tank 16 and are completely submerged in oil 22. It will be appreciated that the minimum oil level is indicated at 24 in the figure. The maximum oil level 26 will illustrate the difference between the oil required to maintain the pump and motor in a submerged condition and the oil required to operate the piston of the hydraulic elevator system. In many configurations more oil is actually required to submerge the motor and pump than is required to run the elevator. Because of this, very large tanks 16 are required to handle the amount of oil. Furthermore, a significant cost is incurred by the reservoiring of so much oil.
Mounted atop tank 16 is a valve block 28 which generally also includes a shut-off valve 30. Valve block 28 is configured to supply low to medium pressure oil at about 12 to 45 bar to the cylinder 32 of the elevator system and allow oil to return to the tank 16 when the elevator car of the elevator system is lowered requiring the bleed-off of pressure from cylinder 32 and piston 34. Since space is an expensive commodity in modem building architecture, machine roomless elevator systems are becoming more accepted and in fact demanded. Because of the size of the hydraulic power unit 10 in a conventional hydraulic elevator system, building a hydraulic elevator system without a machine room has heretofore been nearly impossible. The elevator art is thus in need of a system that allows the hydraulic elevator power unit to be mounted such that a machine room is not required.
The above-identified drawbacks of the prior art are overcome or alleviated by the hydraulic power unit of the invention.
A novel hydraulic power unit is created by vertically configuring various components of the unit and modifying internal structure of the tank thereof in order to maintain oil levels and temperatures required for motor and pump operation while avoiding the necessity of the large volumes of oil required in the prior art. The invention further provides for cooling of the oil reservoir surrounding the motor and pump. Finally the invention provides an insulated cover for the valve block assembly thus ameliorating the noise transmitted through the valve block.
In the vertical configuration made possible by the present invention, the hydraulic power unit of the invention is rendered significantly more compact than its conventional cousin enabling the fitment of the hydraulic power unit in the hoistway with the elevator car. Preferably, the unit is placed in a clearance space between a wall of the hoistway and side of the elevator car. By allowing for in-hoistway containment of the hydraulic power unit, the need for a machine room is obviated.
Since the invention locates the power unit in the hoistway and the machine room is deleted, a conventional rescue pump is inconvenient to use as it requires a technician or rescue personnel to enter the hoistway to operate the same. The invention therefore includes a rescue pump located more conveniently.